Novel antiparasitic agents are well known such as the avermectins disclosed in U.S. Pat. Nos. 4,310,519 and 4,199,569. However, such avermectin compounds, while potent agents against internal and external parasites, are structurally very significantly different from the instant compounds. The avermectins, being macrocyclic agents isolated from an actinomycete, are not related to the instant polycyclic fungal metabolites. In de Jesus et al., J. Chem Soc. Perkin Trans I, pg 697-701 (1984) are described fungal metabolites identified as janthitrems with a polycyclic structure which, however, lacks several structural elements of the instant compounds.